Photomultiplier

An electron multiplier comprising:

• a dynode unit having a plurality of stages of dynode plates stacked in an incident direction of electrons, said dynode plates spaced apart from each other at predetermined intervals through insulating members, each said dynode plate supporting at least one dynode for cascade-multiplying the incident electrons;
• an anode plate for supporting a plurality of anodes, said anode plate having electron through holes through which secondary electrons pass in correspondence with a position where the secondary electrons emitted from a last-stage dynode plate of said dynode unit reach and being arranged to oppose in parallel to said last-stage dynode plate through a first insulating member;
• and
• an inverting dynode plate for supporting at least one inverting dynode for inverting orbits of the secondary electrons passing through said anode plate toward said anode, said inverting dynode plate having a plurality of through holes for injecting a metal vapor to form at least a secondary electron emitting layer on a surface of an each-stage dynode of said dynode unit at positions opposing said anodes, and said inverting dynode plate being arranged to oppose in parallel to said anode plate through a second insulating member such that said anode plate is sandwiched between said last-stage dynode plate of said dynode unit and said inverting dynode plate, each of said through holes in said inverting dynode plate being arranged at a region of said inverting dynode plate other than a region which the secondary electrons passing through said electron through holes of said anode plate reach.